how much work would it involve if we ported the 'rcsim' flight simulator
to our new OpenGL library?

Or, perhaps even better: How about investigating WebGL?

Is a port of your 'rcsim' flight simulator still interesting? I think
the time has come for doing "serious" things in WebGL as the browser
support is now quite good. With Firefox 4.0 we should even be able to
generate some sound. ;-) For me, the obvious thing would be to start
writing a 3d model of the Fokker plane in JSON format, if possible using
a similar scheme as the one used for the tea pot in this article: